(Invited) Amorphous Zr-Doped HfO₂ high-K Dielectric Thin Film for Electronic and Optoelectronic Applications

Abstract

Metal oxides have been used as the high- k dielectric materials in ICs and TFTs for several decades. Recently, they are used as the gate dielectric in the nano-sized MOSFET to take the advantage of the low leakage current and other device properties. HfO 2 is the most popular high- k gate dielectric for sub 1 nm EOT transistors and circuits. One of its main drawbacks is the low crystallization temperature, i.e., < 700°C, which can be a serious reliability problem. We have solved this problem by adding Zr into HfO 2 to form the Zr-doped HfO 2 (ZrHfO) film. This kind of high- k film can remain amorphous after been heated to above 900ºC. The material and electrical properties can be optimized by controlling the concentration of Zr in the film and the post deposition annealing (PDA) condition. In this talk, the author reviews his works in dielectric and non-dielectric applications of the amorphous ZrHfO thin film. They are highly dependent on the structure of the film. The amorphous ZrHfO high- k thin film can be transformed into heterogeneous structures for non-dielectric applications. For example, one or more of the nanocrystalline materials have been embedded into the ZrHfO thin film to serve as charge trapping media. Electrons and holes can be stored in this kind of film separately with the selection of the proper nanocrystal materials and the gate bias condition. This kind of nonvolatile memory device has a lifetime more than 10 years The amorphous ZrHfO high- k thin film can be prepared into another type of heterogeneous structure. After the hard breakdown process, many nano-resistors can be permanently and uniformly formed in the high- k thin film. Light can be emitted from nano-resistors upon the application of a voltage. This is a solid state incandescent light emitting device (SSI-LED) became the principle of light emission is the black body emission. The emitted light has the broad-band spectrum covering the whole visible and part of the near-IR wavelength range. Applications of SSI-LEDs include lighting, on-chip optical interconnect, and others. The nano-resistor structure can also be used as one-time-programmed memory devices, i.e., antifuses, because the leakage current ratio after and before the breakdown process can be larger than 10 5 . Separately, the nano-resistor structure has the current rectification function, which makes it a diode device. However, different from the on-off function of the conventional p-n junction diode, which has a drastic change of the current upon a small increase of the driving voltage, the nano-resistor based diode has the gray-scale capability because of the gradual change of the current vs. voltage curve. There are many other possible applications of the amorphous ZrHfO high- k thin film beyond the conventional electronics and optoelectronics, which will also be discussed. This talk is dedicated to the memory of Prof. Samares Kar for his seminal contribution to this important ECS symposium series.